Expandable motion preservation spacer

ABSTRACT

Embodiments are directed to an expandable spacer for insertion between two adjacent bony structures or two adjacent joint surfaces, and more particularly relate to an expandable spacer for insertion into the void remaining in the intervertebral space. Embodiments may include an expandable spacer comprising a first endplate; a second endplate spaced from the first endplate; and one or more bags disposed between the first endplate and the second endplate that couple the first endplate to the second endplate. The one or more bags may be configured to receive a filler material to expand the expandable spacer from an initial position having a first height to an expanded position having a second height, wherein the second height is greater than the first height.

BACKGROUND

The vertebral or spinal column is a flexible assembly of vertebraestacked on top of each other, extending from the skull to the pelvicbone, which acts to support the axial skeleton and to protect the spinalcord and nerves. The vertebrae are anatomically organized into fourgeneralized body regions identified as cervical, thoracic, lumbar, andsacral. More specifically, the cervical region includes the top of thespine beginning at the skull; the thoracic region spans the torso; thelumbar region spans the lower back; and the sacral region includes thebase of the spine, ending with the connection to the pelvic bone. Withthe exception of the first two cervical vertebrae, intervertebral discs,which are cushion-like discs, separate adjacent vertebrae.

The stability of the vertebral column during compression and movement ismaintained by the intervertebral disc. The intervertebral disc primarilyserves as a mechanical cushion permitting controlled motion betweenvertebral segments of the axial skeleton. The normal disc is a unique,mixed structure, comprised of three component tissues: the nucleuspulpous (“nucleus”), the annulus fibrosus (“annulus”) and two vertebralend plates. The annulus and the nucleus are interdependent, as theannulus contains and secures the nucleus in place, and the nucleusaligns the annulus to accept/distribute external loads. The twovertebral end plates are composed of thin cartilage overlying a thinlayer of hard, cortical bone which attaches to the spongy, richlyvascular, cancellous bone of the vertebral body. The end plates thus actto attach adjacent vertebrae to the disc.

Many factors can adversely alter the composition and structure of theintervertebral disc, such as normal physiological aging, mechanicalinjury/trauma, and/or disease, resulting in impairment or loss of discfunction. Mechanical injury can tear the annulus, allowing the gel-likematerial of the nucleus to extrude into the spinal canal and compressneural elements.

A common procedure for treating damage or disease of the spinal disc orvertebral body may involve partial or complete removal of anintervertebral disc. An implant, which may be referred to as aninterbody spacer, can be inserted into the cavity created where theintervertebral disc was removed to help maintain height of the spineand/or restore stability to the spine. Conventional interbody spacersmay be too large and bulky for introduction into the disc space in aminimally invasive manner, such as may be utilized in a posteriorapproach. Further, these conventional interbody spacers may haveinadequate surface area contact with the adjacent endplates if sized forintroduction into the disc space in a minimally invasive manner. Inaddition, conventional interbody spacers designed for introduction intothe disc space in a minimally invasive manner may not allow motionpreservation; thus, potentially not promoting the desired ease of morenatural movement, expansion, and curvature of the spinal region.

SUMMARY

A first exemplary embodiment provides an expandable spacer that maycomprise a first endplate; a second endplate spaced from the firstendplate; and one or more bags disposed between the first endplate andthe second endplate that couple the first endplate to the secondendplate. The one or more bags may be configured to receive a fillermaterial to expand the expandable spacer from an initial position havinga first height to an expanded position having a second height, whereinthe second height is greater than the first height.

Another exemplar embodiment provides an expandable spacer that maycomprise a first endplate having an exterior side and an interior side,a first main plate seated in the interior side of the first endplate, asecond endplate having an exterior side an interior side, a second mainplate seated in the interior side of the second endplate, a plurality ofbags disposed between the first main plate and the second main plate;and an injection port fixedly attached to the second main plate. Theplurality of bags may couple the first main plate and the second mainplate to one another. The plurality of bags may define a perimeter thatforms a hole. The injection port may be configured to receive a fillermaterial to expand the plurality of bags to place the expanded spacer inan expanded position.

Yet another example embodiment provides method that may compriseinserting an expandable spacer into a void between adjacent vertebrae;and injecting a filler material into the expandable spacer positioned inthe void to cause one or more bags to expand and force apart a firstendplate and a second endplate of the expandable spacer.

BRIEF DESCRIPTION OF THE DRAWINGS

These drawings illustrate certain aspects of some examples of thepresent disclosure, and should not be used to limit or define thedisclosure, wherein:

FIG. 1 is a perspective view of an expandable motion preservation spacershown in an expanded position in accordance with particular embodimentsof the present disclosure;

FIG. 2 is an exploded view of the expandable motion preservation spacerof FIG. 1 in accordance with particular embodiments of the presentdisclosure;

FIG. 3 is a cross-sectional view of the expandable motion preservationspacer of FIG. 1 shown in an expanded position in accordance withparticular embodiments of the present disclosure;

FIG. 4A illustrates a front cross-sectional view of the expandablemotion preservation spacer of FIG. 1 shown in an expanded position inaccordance with particular embodiments of the present disclosure;

FIG. 4B is a close-up view of FIG. 4A taken along box 4B in accordancewith particular embodiments of the present disclosure.

FIGS. 5A, 5B, and 5C illustrate the configuration of a single bag inaccordance with particular embodiments of the present disclosure;

FIGS. 6A and 6B illustrate the first main plate of an expandable motionpreservation spacer in accordance with particular embodiments of thepresent disclosure;

FIGS. 7A and 7B illustrate a second main plate of an expandable motionpreservation spacer in accordance with particular embodiments of thepresent disclosure; and

FIGS. 8A and 8B illustrate a connected first endplate and secondendplate of an expandable motion preservation spacer in accordance withparticular embodiments of the present disclosure.

DETAILED DESCRIPTION

Particular embodiments disclosed herein generally relate to spacers foruse in orthopedic treatments, particularly to implants for insertionbetween two adjacent bony structures or two adjacent joint surfaces, andmore particularly relate to an expandable spacer for insertion into thevoid remaining in the intervertebral space after removal of damaged discmaterial.

In accordance with particular embodiments, the expandable spacerdisclosed herein and methods for its insertion may be used in atreatment protocol for any condition in a patient involving diseased ordamaged bony structures. The patient can be a human being. Additionally,it is contemplated that the expandable spacer may be useful inveterinary science for any animal having adjacent bony structures to befused. The expandable spacer may be inserted into a space through asmall incision and narrow pathways using appropriate minimally invasivetechniques, positioned across the space, and expanded to the desiredheight. The incision may be short, for example, about one inch inlength, smaller than the implant in an expanded configuration. If thedesired position and/or expansion are not achieved, the expandablespacer may be collapsed, repositioned, and expanded in situ.

FIG. 1 is a perspective view of an expandable spacer 100 shown in anexpanded position in accordance with some embodiments of the presentdisclosure. In the embodiment depicted, the expandable spacer 100includes a first side 102 and a second side 104, wherein a firstendplate 106 may be situated at the first side 102, and wherein a secondendplate 108 may be situated at the second side 104. The first endplate106 may have an exterior side 110 and an interior side 112. Similarly,the second endplate 108 may also have an exterior side 114 and aninterior side 116. The exterior sides 110, 114 of the first and secondendplates 106, 108 may include a plurality of protrusions 118, 120affixed thereto. Although not shown in FIG. 1, the interior side 112 ofthe first endplate 106 may be configured so that a first main plate 122(e.g., shown on FIG. 2) may be seated therein. Similarly, the secondendplate 108 may be configured so that a second main plate 124 may beseated therein. The second main plate 124 may include an injection port126 fixedly attached thereto. One or more bags (e.g., first bag 128) maybe positioned between the first main plate 122 (not shown in FIG. 1) andthe second main plate 124.

In accordance with particular embodiments, the expandable spacer 100allows for separation of the first endplate 106 from the second endplate108 by injecting a filler material into the one or more bags (e.g.,first bag 128) and/or a hole formed inside the one or more bags (e.g.hole 144 on FIG. 2). By way of example, the filler material may beinjected through the injection port 126 disposed on the second mainplate 124. Injection of the filler material may facilitate expansion ofthe expandable spacer 100 from an initial position (e.g., closed orcompressed) to an expanded position based, for example, on the amount offiller material injected. Suitable filler materials may include asynthetic or natural nucleus material including, but not limited to, asaline solution, silicone gel, poly(dimethylsiloxane) (PDMS) or Low MWpoly(dimethylsiloxane), Poly(ethyleneoxide-copropyleneoxide)(PEO-PPO),Poly(vinylalcohol). The one or more bags (e.g., first bag 128) mayconnect the first and second endplates 106, 108, thereby ensuringcapsulation of the filler material at a designed pressure. The pressuremay be about 0.1 MPa to about 1.5 MPa. Alternatively, the pressure maybe about 0.05 MPa to about 5 MPa, about 0.01 MPa to about 10 MPa.

In some embodiments the expandable spacer 100 may be expanded parallelor with a lordotic angle, depending on how the one or more bags (e.g.,first bag 128) are attached to the first endplate 106 and/or the secondendplate 108. Particular embodiments of the expandable spacer 100 mayhave an initial position (e.g., a closed or compressed form) and anexpanded position. The initial position may have an initial height andlordosis. For example, the initial position may have a height of about 4mm to about 10 mm. Alternatively, the initial position may have a heightof about 4 mm to about 10 mm, about 5 mm to about 9 mm, about 6 mm toabout 8 mm. The initial position may have an initial lordosis of about 0degrees to about 6 degrees. Alternatively, the initial position may havea lordosis of about 0 degrees to about 6 degrees, about 1 degree toabout 5 degrees, or about 2 degrees to about 4 degrees.

Embodiments disclosed herein may be expanded to a predefined parallel orlordotic forms. The expanded position of the expandable spacer may havea height of about 5 mm to about 15 mm. Alternatively, the expandedposition of the expandable spacer may have a height of about 6 mm toabout 14 mm, about 7 mm to about 13 mm, or about 8 mm to about 12 mm.The expanded position of the expandable spacer may have a lordosis ofabout 4 degrees to about 10 degrees, about 5 degrees to about 9 degrees,or about 6 degrees to about 8 degrees. At maximum height, someembodiments disclosed herein may include a mechanism, such as a stop, toprevent the first and second endplates from sliding freely. This is asafety feature, ensuring the safe operation of the expandable spacer 100at its maximum height.

Any one or all of the members of the expandable spacer 100 may be madefrom any suitable biocompatible material, including synthetic or naturalautograft, allograft or xenograft tissues, and may be resorbable ornon-resorbable in nature, Examples of tissue materials include hardtissues, connective tissues, demineralized bone matrix, and combinationsthereof. Further examples of resorbable materials are polylactide,polyglycolide, tyrosine-derived polycarbonate, polyanhydride,polyorthoester, polyphosphazene, calcium phosphate, hydroxyapatite,bioactive glass, and combinations thereof. Further examples ofnon-resorbable materials are non-reinforced polymers, carbon-reinforcedpolymer composites, PEEK and PEEK composites, shape-memory alloys,titanium, titanium alloys, cobalt chrome alloys, stainless still,ceramics, and combinations thereof, as well as others.

The expandable spacer 100 may be manufactured using any method formaking similar objects. Particularly applicable are methods for moldingplastics, for example, injection molding or blow molding. Alsoapplicable are methods for cutting metal and/or for making metal parts,for example, shearing, laser cutting apparatus, and waterjets. Theimplant may be manufactured as a whole or fabricated from individualparts. The parts may be snapped or welded together in a number ofdifferent ways.

After assembly, the expandable spacer 100 may be sterilized andpackaged. Sterilization may be accomplished by autoclave, ultravioletlamp, bleach solutions, alcohol solutions, and/or combinations thereof.The expandable spacers may be packaged individually or in groups, usingany material suitable for packaging medical items.

Methods for using the expandable spacer 100 are also disclosed herein.Although methods disclosed herein are suitable for fusion of vertebrae,the expandable spacer 100 may also be suitable for fusion of anyadjacent bones or joints, such as the ankle or knee. The methods may notbe limited to the embodiments described herein.

After anesthetizing the patient, a surgical incision may be made toaccess the two adjacent vertebrae to be fused in the patient's body. Thesurgeon may use a posterior approach, anterior approach, lateralapproach, or any other approach deemed appropriate for the patient. Theaccessed space between the vertebrae may be prepared for insertion ofthe expandable spacer 100. The surgeon may do one or more of thefollowing: discectomy, dissect and remove bone, and reposition or removecartilage, including removal of all or part of the vertebral endplatesand/or cortical bone. The expandable spacer 100 may then be insertedinto the prepared space using any suitable technique, for example, theexpandable spacer 100 can be inserted to the space through a cannula inan initial form. In some embodiments, the insertion may be monitored,for example, using an endoscope. After insertion, the filler materialmay be injected into the one or more bags (e.g., first bag 128). As thefiller material is injected, the bags should expand causing the firstendplate 106 and the second endplate 108 to move away from one anotherother, resulting in expansion of the expandable spacer 100.

In order to expose the cancellous bone, removal of all or part of thevertebral endplates and cortical bone layer can be done. In someembodiments, the expandable spacer 100 may be in contact with the bonemarrow as the bone marrow provides osteoprogenitor cells which enhancethe growth and formation of new bone. When proper distraction isachieved, the expandable spacer 100 may be adjusted to a therapeuticallyacceptable height for the patient. A “therapeutically-acceptable” heightmay be any height that provides beneficial to the patient, e.g., reducedpain, reduced pressure on nerve roots, restoration of joint function,restoration of motion, and/or repair of diseased or injured condition.The expandable spacer 100 may be collapsed and reextended if necessary,for a better fit if the insertion is not secure or the height may beincorrect, or a condition in the patient changes.

Moreover, after surgery if the expandable spacer 100 needs anyreadjusting or repositioning, the expandable spacer 100 may be accessedand adjusted via a minimally invasive procedure. Thus, the need forreplacement of the expandable spacer 100 may be decreased, and in turn,decreasing pain and costs for the patient may be realized. Although theexpandable spacer 100 may not require any supplemental fixation withdevices such as rods, screws, and additional plates, these devices maybe ultimately used. When the expandable spacer is positioned and securedin the desirable manner, the surgical incision may be closed, and thepatient may be allowed to heal.

FIG. 2 is an exploded view of the expandable spacer 100 of FIG. 1 inaccordance with some embodiments of the present disclosure. As depicted,the expandable spacer 100 may include a first endplate 106, a first mainplate 122, a first bag 128, a second bag 160, a second main plate 124,and a second endplate 108. As depicted, the first main plate 122 may becoupled to the first endplate 106. For example, the interior side 112 ofthe first endplate 106 may be configured so that the first main plate122 may be seated therein. The first main plate 122 may include anexterior side 132 and an interior side 134. In some embodiments, grooves136 may be disposed at or around the perimeter of the first main plate122. The first and second bags 128, 130 may be configured to be seatedin the grooves 136 formed in the first main plate 122. As depicted, thesecond main plate 124 may be coupled to the second endplate 108. Forexample, the interior side 116 of the second endplate 108 may beconfigured so that the second main plate 124 may be seated therein. Thesecond main plate 124 includes an interior side 140 and an exterior side142, wherein a housing 146 may be affixed at or near the center thereof,on the interior side 140. Although not shown in FIG. 2, the housing 146may be configured to receive, by slidable engagement, an extension 148(e.g., FIGS. 3 and 6A) from the interior side 134 of the first mainplate 122. In some embodiments, grooves 138 may be disposed at or aroundthe perimeter of the second main plate 124. The first and second bags128, 130 may be configured to be seated in the grooves formed in thesecond main plate 124. Both the first and second endplates 106, 108 mayhave protrusions 118, 120 disposed on their exterior sides 110, 114.

As depicted, the one or more bags (e.g., the first and second bags 128,130) may define a perimeter that defines a hole 144. In someembodiments, the first and second bags 128, 130 may be concentric. Forexample, the second bag 160 may be placed inside the first bag 128 withthe first bag 128 defining a perimeter that surrounds the second bag160. The one or more bags (e.g., first and second bags 128, 130) may beconstructed from any suitable material. Suitable materials may include,for example, polytetrafluoroethylene (PTFE), extended-PTFE,Poly(propylene) (PP), Poly(ethylene terphthalate) (PET). The one or morebags (e.g., first and second bags 128, 130) may have any suitable shape.For example, suitable shapes may include, but are not limited to,toroids, polyhedrons, and variations thereof. In some embodiments, thesuitable shape may include a polyhedron with rounded corners and/oredges. In some embodiments, the suitable shape may include an annularshape with straight side and rounded corners and/or edges. In someembodiments, the suitable shape may define a perimeter defining the hole144.

FIG. 3 is a cross-sectional view of the expandable spacer 100 of FIG. 1in accordance with particular embodiments shown in an expanded position.As depicted in FIG. 3, the expandable spacer 100 may include a firstplate 102 and a second plate 116 connected by first and second bags 128,130. As previously described, the first and second bags 128, 130 may besecured in the grooves 136 formed in the first main plate 122 and alsosecured in the grooves 138 formed in the second main plate 124. Asdepicted, the first main plate 122 may include an extension 148 from theinterior side 134. In some embodiments, the extension 148 may bereceived in a housing 146 that extends from an interior side 140 of thesecond main plate 124. In some embodiments, the housing 146 may beconfigured to receive the extension 148 by slidable engagement. Bysecuring the extension 148 in the housing 146 expansion of theexpandable spacer 100 may be controlled, reducing the tendency of thefirst plate 102 and the second plate 116 from becoming misaligned duringexpansion.

FIGS. 4A and 4B illustrate a front cross-sectional view of theexpandable spacer 100 of FIG. 1 shown in an expanded position. FIG. 4Ais a front cross-sectional view of the expandable spacer 100 of FIG. 1shown in an expanded position. FIG. 4B is an enlarged view of FIG. 4Ataken along box 4B. As depicted, the one or more bags (e.g., first bag128 and second bag 160) may include multiple skins, shown as first outerskin 150 a, second outer skin 150 b, first inner skin 152 a, and secondinner skin 152 b. By way of example, the first bag 128 may include afirst outer skin 150 a and a first inner skin 152 a. The first outerskin 150 a and the first inner skin 152 a may define a first interiorvolume 154 of the first bag 128 that receives the filler material forfilling and expanding the first bag 128. By way of further example, thesecond bag 160 may include a second outer skin 150 b and a second innerskin 152 b. The second inner skin 150 b and the second inner skin 152 bmay define a second interior volume 156 for receiving the fillermaterial for filling and expanding the second bag 160. The second bag160 may also formed a perimeter defining hole 144 that can also receivethe filler material. Thus, the filler material may be introduced intothe hole 144, the first interior volume 154, and/or the second interiorvolume 156.

In some embodiments, the first outer skin 150 a and first inner skin 152a may be secured to one another to form the first bag 128 and the secondouter skin 150 b and the second inner skin 152 b may be secured to oneanother to form the second bag 160. Any suitable technique may be usedfor securing the skins to one another for forming the first and secondbags 128, 130, respectively. Suitable techniques may include, forexample, adhesives, stitching, or heat melding among others. In someembodiments, the first outer skin 150 a and the first inner skin 152 amay extend upward through the grooves 136 in the first main plate 122and may be further secured in place with stitches 158. The stitches 158may hold the first inner outer skin 150 a the first outer skin 112together forming the first bag 128. In some embodiments, the secondouter skin 150 b and the second inner skin 152 b may extend upwardthrough the grooves 136 in the first main plate 122 and may be furthersecured in place with stitches 158. The stitches 158 may hold the secondouter skin 150 a the second outer skin 112 together forming the firstbag 128. As depicted, the stitches 158 for both the first bag 128 andthe second bag 160 may be disposed between the first plate 102 and thefirst main plate 122. The stitches 158 may be made from any suitablematerial. For example, the stitches 158 may comprise a biocompatiblematerial, such as Poly(propylene) (PP), Poly(ethylene terphthalate)(PET) or Poly(tetrafluroethylene) (PTFE). While the precedingdescription describes use of separate skins (e.g., first outer skin 150a and first inner skin 152 a) for forming the one or more bags, itshould be understood that that the bags (e.g., first bag 128 and secondbag 160) may be otherwise formed. For example, the one or more bags mayeach be formed from a continuous skin. In addition, while separate bags(e.g., first bag 128 and second bag 160) are shown, the one or more bagsmay be a single bag that is configured to define one or more interiorvolumes (e.g., first interior volume 154, second interior volume 156,etc.) for receiving the filler material.

FIGS. 5A, 5B, and 5C illustrate another embodiment of the expandablespacer 100 that utilize a single bag 160. FIG. 5A is a perspective viewof the expandable spacer 100 showing a single bag 160. As depicted, theexpandable spacer may include a first main plate 122, a second mainplate 124, and first bag 128. For simplicity, the first plate 102 (e.g.,shown on FIG. 1) and the second plate 116 (e.g., shown on FIG. 1) arenot depicted on FIG. 5A. As depicted in FIG. 5A, the single bag 160 maybe disposed between the first main plate 102 and the second main plate124. In some embodiments, the injection port 126 on the second mainplate 124 allows for the injection of filler material into theexpandable spacer 100, for example, into the single bag 160 and/or thehole 144 defined by the single bag 160.

Referring to FIGS. 5B and 5C, partial cross-sectional views of theexpandable spacer 100 of FIG. 5A are shown, in accordance withparticular embodiments of the present disclosure. In FIG. 5C, theexpandable spacer 100 is shown without the top main plate 122 forsimplicity. As depicted in FIGS. 5B and 5C, the single bag 160 mayinclude a first outer skin 150 c and a first inner skin 152 c. Asdepicted, the first outer skin 150 c and the first inner skin 152 cdefine an interior volume 162 of the single bag 160 that can be filledwith a filler material for expansion of the single bag 160, therebyexpanding the expandable spacer 100. In some embodiments, the firstouter skin 150 c and the second outer skin 152 c may extend into grooves136 formed in the first main plate 122. With specific reference to FIG.5B, the first outer skin 150 c and the second outer skin 152 c mayextend through the exterior side 132 of the first main plate 122 withstitches 158 securing the first outer skin 150 c and the second outerskin 152 c to one another. At the second main plate 124, the single bag160 may be secured in grooves 138 formed in the second main plate 124.For example, the first outer skin 150 c and the second outer skin 112may extend into and be secured in the grooves 138 in the second mainplate 124. The second main plate 124 may also include a housing 146 thatextends from an interior side 140 and is configured to receive theconnector 126 from the first main plate 122.

FIGS. 6A and 6B illustrate a first main plate 122 of an expandablespacer 100 (e.g., shown on FIG. 1) in accordance with particularembodiments of the present disclosure. FIG. 6A is a perspective view ofthe first main plate 122 in accordance with particular embodiments. FIG.6B is a top plan view of the first main plate 122 in accordance withparticular embodiments. As shown in FIG. 6A, the first main plate 122may include grooves 136 disposed at or near the perimeter thereof, onthe exterior side 132. As depicted, the grooves 136 may be radiallyspaced. As previously described, the grooves 136 may receive skins(e.g., first outer skin 150 a shown on FIG. 4A, first inner skin 150 ashown on FIG. 4A, etc.) that form the one or more bags (e.g., first bag128 on FIG. 1). While obstructed from view on FIGS. 6A and 6B, thegrooves may extend through the exterior side 132 to the interior side134. The number of grooves 136 may be selected, for example, based onthe number of the one or more bags required for a specific application.Moreover, also depicted is the extension 148 that may be disposed on theinterior side 134 of the first main plate 122, where the extension 148may be attached at or near the center thereof. For the embodiment shown,the extension 148 may be slidably connected to the housing 146 (e.g.,shown on FIG. 7A). The extension 148 may be a variety of shapes andsizes, depending upon the specific procedure.

FIGS. 7A and 7B illustrate a second main plate of an expandable spacer100 (e.g., shown on FIG. 1) in accordance with particular embodiments ofthe present disclosure. FIG. 7A is a perspective view of the second mainplate 124 in accordance with particular embodiments. FIG. 7B is a topplan view of the second main plate 124 in accordance with particularembodiments. As shown, the second main plate 124 may include grooves 138disposed at or near the perimeter thereof. As depicted, the grooves 138may be radially spaced. As previously described, the grooves 138 mayreceive skins (e.g., first outer skin 150 a shown on FIG. 4A, firstinner skin 152 a shown on FIG. 4A, etc.) that form the one or more bags(e.g., first bag 128 on FIG. 1). The number of grooves 138 may selected,for example, based on the number of the one or more bags required for aspecific application. Moreover, also depicted is the housing 146 thatmay extend from the interior side 140 of the second main plate 124,where the housing 146 may be attached at or near the center thereof. Forthe embodiment shown, the housing 146 may be slidably connected to theextension 148 (e.g., shown on FIGS. 6A and 6B). The housing 146 may be avariety of shapes and sizes, allowing for slidable connection with theextension 148. Also shown in FIG. 7A is the injection port 126, wherebythe injection port 126 may be fixedly attached to the second main plate124. The injection port 126 allows injection of the filler material intothe one or more bags (e.g., first bag 128 on FIG. 1) for expansion ofthe expandable spacer 100. In some embodiments, the injection port 126may be sealed by a screw or similar attachment device (not shown).

FIGS. 8A and 8B illustrate a connected first endplate 106 and secondendplate 108 of an expandable spacer 100 in accordance with particularembodiments of the present disclosure. FIG. 8A is a front plan view ofthe first endplate 106 and the second endplate 108 of the expandablemotion preservation spacer 100 in a collapsed position. FIG. 8B is afront plan view of the first endplate 106 and the second endplate 108 ofthe expandable spacer 100 in an expanded position. In the embodimentshown, the one or more bags (e.g., first bag 128 shown on FIG. 1) arenot depicted for the purpose of showing the expansion area of theexpandable spacer 100. The expandable spacer 100 may be suitable forinsertion into a patient's intervertebral space to restore the heightand shape of the space.

As depicted, the expandable spacer 100 has a first height H1 in thecollapsed position (e.g., see FIG. 8A) and a second height H2 in theexpanded position (e.g., see FIG. 8B). In an initial position (orcompressed position), for example, the extension 148 may be seatedcompletely inside of the housing 146. After the injection of the fillermaterial into the injection port 126, the filler material may flow intothe expandable spacer 100. The introduction of the filler material intothe expandable spacer 100 should result in expansion of the one or morebags (e.g., first bag 128 and second bag 160 shown on FIG. 2).Subsequently, the one or more bags may vertically lift causing the firstand second endplates 106, 108 to move away from another and expand theexpandable spacer 100. From the initial position shown in FIG. 8A, theexpansion may cause the first and second endplates 106, 108 to move awayfrom one another. In its expanded position, as depicted in FIG. 8B, theextension 148 may no longer be completely seated within the housing 146.Moreover, in addition to providing flexible movement along the verticalaxis, the expandable spacer 100 may also be capable of movement in thehorizontal direction, therefore allowing for flexible side-to-side andback-and forth movement. Thus, the expandable spacer 100 may provide formore natural vertebral movement.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. An expandable spacer comprising: a firstendplate; a second endplate spaced from the first endplate; and one ormore bags disposed between the first endplate and the second endplatethat couple the first endplate to the second endplate; wherein the oneor more bags are configured to receive a filler material to expand theexpandable spacer from an initial position having a first height to anexpanded position having second height, wherein the second height isgreater than the first height.
 2. The expandable spacer of claim 1,further comprising a first base plate that is received in the firstendplate, wherein the one or more bags are secured to the first baseplate.
 3. The expandable spacer of claim 1, wherein the one or more bagseach comprise an inner layer and an outer layer that extend throughgrooves formed in the first base plate, the inner layer and the outerlayer being secured to one another by stitches disposed between thefirst base plate and the first endplate.
 4. The expandable spacer ofclaim 1, further comprising a second base plate that is received in thesecond endplate, wherein the one or more bags are secured to the secondbase plate.
 5. The expandable spacer of claim 1, further comprising afirst base plate coupled to the first endplate and a second base platecoupled to the second endplate, wherein the one or more bags are securedto the first base plate and the second base plate.
 6. The expandablespacer of claim 4, wherein the first base plate comprises an extensionfrom an interior side of the first base plate, and wherein the secondbase plate comprises a housing that extends from an interior side of thesecond plate and that slidably receives the extension from the firstbase plate.
 7. The expandable spacer of claim 1, wherein the one or morebags form a perimeter that defines a hole.
 8. The expandable spacer ofclaim 7, wherein the one or more bags comprise a first bag and secondbag that are concentric, wherein the first bag and the second bag eachindividually comprise an internal layer and an external layer.
 9. Theexpandable spacer of claim 1, wherein the one or more bags are generallyannular in shape.
 10. The expandable spacer of claim 1, wherein theinitial height is about 2 mm to about 10 mm, and wherein the secondheight is about 8 mm to about 14 mm.
 11. The expandable spacer of claim1, wherein the initial position of the expandable spacer has a lordosisof about 0 degrees to about 6 degrees, and wherein the expanded positionhas a lordosis of about 4 degrees to about 10 degrees.
 12. An expandablespacer comprising: a first endplate having an exterior side and aninterior side; a first main plate seated in the interior side of thefirst endplate; a second endplate having an exterior side an interiorside; a second main plate seated in the interior side of the secondendplate; a plurality of bags disposed between the first main plate andthe second main plate that couple the first main plate and the secondmain plate to one another, wherein the plurality of bags defines aperimeter that forms a hole; and an injection port fixedly attached tothe second main plate, wherein the injection port is configured toreceive a filler material to expand the plurality of bags to place theexpanded spacer in an expanded position.
 13. The expandable spacer ofclaim 12, wherein the plurality of bags each comprise an inner layer andan outer layer that extend through grooves formed in the first baseplate, the inner layer and the outer layer being secured to one anotherby stitches disposed between the first base plate and the firstendplate.
 14. The expandable spacer of claim 12, wherein the first baseplate comprises an extension from an interior side of the first baseplate, and wherein the second base plate comprises a housing thatextends from an interior side of the second base plate and that slidablyreceives the extension from the first base plate.
 15. The expandablespacer of claim 12, wherein the plurality of bags comprises a first bagand second bag that are concentric, wherein the first bag and the secondbag each individually comprise an internal layer and an external layer.16. The expandable spacer of claim 12, wherein the expandable spacer hasan initial height of about 2 mm to about 10 mm, and wherein theexpandable spacer has a second height in the expanded position of about8 mm to about 14 mm.
 17. The expandable spacer of claim 16, wherein theinitial position of the expandable spacer has a lordosis of about 0degrees to about 6 degrees.
 18. The expandable spacer of claim 16,wherein the expanded position of the expandable spacer has a lordosis ofabout 4 degrees to about 10 degrees.
 19. A method comprising: insertingan expandable spacer into a void between adjacent vertebrae; andinjecting a filler material into the expandable spacer positioned in thevoid to cause one or more bags to expand and force apart a firstendplate and a second endplate of the expandable spacer.
 20. The methodof claim 19, wherein the one or more bags are coupled to a first mainplate seated in the first endplate and wherein the one or more bags arecoupled to a second main plate seated in the second endplate, wherein anextension from an interior side of the first main plate slides in ahousing that extends from an interior side of the second main plate whenthe first endplate and the second endplate are forced apart.